Direction finder



Aug. 26, 1947. H. BUSIGNIES DIRECTION FINDER Fi led Dec.

11, 1942 2 Sheets-Sheet 2 INVENTOR. 'HENP/ 6. BUS/GN/ES Patented Aug. 26, 194'? DIRECTION FINDER Application December 11, 1942, Serial No. 468,668

6 Claims.

This invention relates to direction finders, and more particularly to direction finders provided with sensing antenna designed to operate over a relatively wide frequency band.

In the past, many system have been proposed for combining the effect of a sensing antenna with a directional antenna for the purpose of obtaining a uni-directional effect. This problem is relatively simple when the antennae are designed to operate at a single frequency. However, when it is desired to operate over a wide band of frequencies the relative phase shift in the transmission lines coupling the directive antenna and the omni-directional sensing antenna to a common translator device differs with different wavelengths. Accordingly, a system designed to produce the necessary 90 phase shiftat one frequency will not produce the proper phase shift at a different frequency.

Moreover, the effective height of the directive system decreases with the frequency and the effective height of the omni-directional antenna remains constant throughout the frequency shifts. Accordingly, there is generally required an adjustment in amplitude between the energy obtained from the directional system if the frequency is varied.

It is a principal object of my invention to provide a directive antenna system and a sensing antenna, in which the desired phase relation will be maintained between the out-puts of the two antennae over a relatively wide frequency band.

It is a further object of my invention to provide a uni-directional antenna system comprising a directional antenna and a sensing antenna, wherein proper phase relation and amplitude relation of the energy from the two antennae will remain constant over a relatively wide frequency band.

It is a still further object of my invention to provide a direction finder in which the desired phase and amplitude relationship will be maintained between the energy from the directive and sensing antenna over a wide frequency band without the necessity of any manual adjustment.

According to a feature of my invention, I provide a direction finder of the type having two spaced antenna elements coupled together in phase opposition to provide a directive antenna and an omni-directional unit used as a sensing antenna. A pair of conductor lines form at least a part of one of the transmission lines coupling the omni-directional or the directional antenna made longer and shorter in length from the length of the line coupling the other antenna to the device by equal amounts, and are coupled together at their ends remote from the antenna in phase opposition. At the junction point of these two lines the coupling to the translator is effected, either directly or through a further transmission line. Since the two conductor lines differ in lengths by equal amounts, a phase advance will be effected at the remote terminal of one line and an equal phase delay at the corresponding terminal of the other line. By combining energy from these lines in phase opposition, a resultant shift in phase is accomlished, bringing the energy at this junction point into phase coincidence with the energy from the other line at the translator.

In order that the proper amplitude relationship be maintained throughout the band of frequencies, it is desirable that the two conductor lines differ in length by an amount equal to the spacing between the two antenna units forming the directive antenna, or close to this value, taking into account the lower speed of the wave into the high frequency lines.

A better understanding of my invention and the objects and features thereof may be had by reference to the accompanying drawings, in which:

Fig. 1 is a diagram of an embodiment of my invention;

Figs. 2 and 3 are vector diagrams demonstrating the principles of my invention;

Fig. 4 illustrates a modified form of my invention applied to a different antenna system;

Fig. 5 is a still further modification of my invention applied to a loop antenna arrangement; and.

Fig. 6 is a still further modification of my invention.

Turning first to Fig. 1, the directional antenna comprises two mono-polar antenna units DI, D2 spaced apart a distance d, and coupled together in phase opposition by means of transmission line Ll provided with a transposition T. Decouplers may be provided, if desired, at M and 5.6 to couple line Ll with antenna elements DI and D2, respectively. I use the term decoupler for these circuits in preference to the term coupler since the decoupling effect of the coupling unit is directly in point in these circuits. These coupling units or decouplers, are preferably of the type described more fully in the copending application of A. G. Richardson and myself, Serial No. 440,154, filed April 23, 1942. The midpoint of line Ll is coupled over a line L2, transformer H, and transmission line ll! to receiver i3.

Sensing antenna Si is coupled through a decoupler [5, two transmission conductor lines L3 and L4, joined together in phase opposition at junction point I 'i by reason of a transposition l8; transformer l2, which together with transformer ll, may be considered as a common translator; and transmission line H] to the same receiver l3. Conductor lines L3 and L4 are made respectively longer and shorter than line L2 by equal amounts, and conductors Ll, L and L5 are made of the same length.

Turning to Figs. 2 and 3, the operation of the system described may be more clearly understood. In Fig. 2 is illustrated a vector diagram for the directional antenna arrangement DI, D2, Li.

angles to the plane of the drawing, the energy in each of the units will be vectorially in the same direction. As shown in dotted lines in Fig. 2 the vectors RDi and RDZ will be of equal amplitude and opposite polarity, so that no energy is applied to line L2. This corresponds to the zero or null position of the direction finding unit. However, when the wave approaches the antenna arrangement in the plane of the drawing corresponding to maximum reception, vectors R131 and RD?! will be rotated to a position as shown in solid lines in Fig. 2, producing a resultant directional vector RD. At the same time, energy in omnidirectional antenna Si will produce the vector RSI in antenna SI as shown in dotted lines in Fig. 3. However, at junction point ll two vectors, as shown at R4L and R-BL, would be produced in the absence of a transposition, because of the phase shift caused in the unequal-length lines L3, L4. With the transposition, however, the vectors will be in the positions shown in solid lines at R4L and R3L+ 180, producing a resultant vector REL which is in phase with the directive vector RD of Fig. 2. It is thus clear that the arrangement of transmission lines produces the necessary 90 phase shift to produce the proper ene'rgization for sensing purposes. However, if lines L3 and L4 are designed merely for this relationship without amplitude considerations, the amplitude of vector R5L will vary with respect to RD with the change in wavelength. In order that the amplitude relationship may be maintained substantially constant, it is desirable that lines L3 and L4 be of such length that their difference in length is equal to the space d between directional units Di and D2. In order that the same amplitude may be obtained in the two channels, the energy sent over the two branches of line LI and over lines L3 and L4 should be the same. Therefore, the decoupler devices I4, 55 and It should be designed to apply the same voltage across the lines at all frequencies.

It is not necessary that the directional unit be of the type shown in Fig. 1, as the directional unit may take other forms such as the form of the dipole units shown in Fig. 4, for example. In this figure are shown four dipole antenna units 2|, 22, 23 and 24 in pairs arranged at right angles to one another and coupled together by transmission lines 25, 26, respectively through coupling units 1,2, 3 and 4 made of transformers or vacuum tubes. Lines 25 and 26 are in turn coupled by additional lines 2'1, 28 to a goniometer shown diagrammatically at 29. A sensing antenna 55 is provided with coupler 5, cou- It should be understood that when energy approaches the system from a direction at right pled over a line 3|, decoupler unit 32, conductor lines 33, 34, transformer 35 and switch 36 to the common input transformer 3'1. At the same time it should be noted that instead ,of providing two separate full length transmission lines such as shown at L3 and L4 of Fig. 1, shorter transmission lines 33 and 34 which difier in length by half of the spacing between antenna units 2! and 22 (or 23 and 24) is provided. Line 3| may be of any length provided it is so related to each of lines 2'! and 28 that the sum of the lengths separately measured from antenna 39 to the common coupling point '37 over the two branch lines 33 and 34 is equal to twice the length of either line 2'! or 28, combined with coupling unit 38 measured to an associated antenna unit. The presence of the coupling unit 32 may afiect the operation of the sense line differently from the operation of the two other lines. It may be necessary to introduce at the same distance two coupling units 32A and 32B of the same type and the two other lines as shown on the drawings. It should be distinctly understood that lines in the form shown at L3, L4 of Fig. 1 may be used in place of the combined arrangement 3!, 33, 34 of Fig. 4, if desired, and that the directive arrangement of Fig. 4 may readlly be substituted in the system of Fig. 1.

Fig. 5 illustrates a still further embodiment of my invention utilizing a loop antenna 55 used as the directional antenna system. The vertical sides 5i, 52 of loop may be considered as the antenna pick-up elements since they are the ones effective in direction finding. These elements 5i, 52 are coupled together in phase opposition to a transmission line 53 extending to the common coupling unit 54. Sensing antenna 55 is provided with a decoupler 56 which, in turn, is coupled to translater means 54 over the pair of lines 51, 58 and further line 59. In this instance, lines 51 and 58 are made of such a length that the difference therein is equal to the spacing between 5| and 52, and the over-all length of lines 5'1, 59, and 58, 59 is equal to twice the length of line 53. If complete equality of amplitude is not required, the difference of length can be made larger than the spacing in order to obtain more energy fromv the sense antenna.

The omni-directional antenna system of Fig. 5 may be substituted for the corresponding antenna systems in either Figs. 1 or 4, and similarly the directional antenna system of Figs. 1 and 4 may be substituted for that of Fig. 5, if desired.

The arrangement of Fig. 6 is similar to that of Fig. 5 using vertical antenna units in place of a loop. In this figure the directive antenna comprises two antenna units 6!), 6| coupled together in phase opposition over decouplers 62, 63 and lines L55, L5I. The junction point of lines L55, L5I is coupled by lines L55 to common coupling means 68. Sensing antenna 65 is coupled over decoupler 66 and lines L52, L53, L54 to the same common'coupling means 68. The relation of the lines may be simply expressed as follows:

L5D=L5l V L52-L53=L5ll+L5| (more generally the spacing between antenna 60, 6|);

q L u mgiemw In the examples illustrated, I have shown the phase corrector network applied in the line between the sensing antenna and the translator.

It is clear that 'phase correction may be had by applying networks of this type to the directional unit instead. However, this reverse arrangement is generally less desirable since only phase correction without amplitude compensation results.

The sense indication of the direction finder made in accordance with the principles of my invention will operate over a wide frequency band, it being necessary only that the spacing between the elements of the directive unit be not greater than a half wavelength at the highest frequency of the band to be covered by the system in accordance with my invention, for example, a frequency ratio of as high as ten to one may be readily received while maintaining proper phase and amplitude relation between the energy from the directive and sensing antenna units.

While I have described above the principles of my invention in connection with specific apparatus, and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth in the objects of my invention and the accompanying claims.

What is claimed is:

1. In a direction finder of the type having two spaced antenna means coupled together in phase opposition to provide a directional antenna, a translator, a transmission line coupling said directional antenna system to said translator, an omni-directional sensing antenna, and a second transmission line for coupling said omni-directional antenna to said translator, the combination of means for assuring in-phase relationship between energy from said omni-directional antenna and from said directional antenna system in said translator device, comprising a pair of conductor lines forming at least a part of one of said transmission lines intermediate one of said antennae and said translator, said conductor lines differing in length, and being coupled together co-phasally at their ends arranged nearest said one antenna and in phase opposition at their ends remote from said one antenna, the combined electrical lengths of the transmission line including said pair of conductor lines as measured from said one antenna to said translator along both conductor lines of said pair being substantially equal to twice the length of the transmission line between the other antenna and said translator.

2. In a direction finder of the type having two spaced antenna means coupled together in phase opposition to provide a directional antenna, a translator, a transmission line coupling said directional antenna system to said translator, an omni-directional sensing antenna, and a second transmission line for coupling said omni-directional antenna to said translator, the combination of means for assuring in-phase relationship between energy from said omni-directional antenna and from said directional antenna system in said translator device, comprising a pair of conductor lines forming at least a part of one of said transmission lines intermediate one of said antennae and said translator, said conductor lines diifering in length by the spacing between said spaced antenna means, and being coupled together co-phasally at their ends arranged nearest said one antenna and in phase opposition at their ends remote from said one antenna, the combined electrical lengths of the transmission line including said pair of conductor lines as measured from said one antenna to said translator along both conductor lines of said pair being substantially equal to twice the length of the other transmission line between the other antenna and. said translator.

3. A direction finder according to claim 2, wherein said conductor lines are made longer and shorter, respectively, than the transmission line between said other transmission line by half the spacing between said spaced antenna means.

4. A direction finder according to claim 2, wherein said conductor lines are relatively short with respect to the total length of the corresponding transmission line, and are coupled at their near end to said one antenna by a decoupler device, and at their remote ends over a length of transmission line to said translator.

5. A direction finder according to claim 2, wherein said conductor lines are relatively short with respect to the total length of the corresponding transmission line and are coupled at their near end to said one antenna by a length of transmission line and a decoupler, and at their remote ends to said translator by a coupling coil.

6. In a direction finder of the type having two spaced antenna means coupled together in phase opposition to provide a directional antenna, a translator, a transmission line coupling said directional antenna system to said translator, an omni-directional sensing antenna, and a second transmission line for coupling said omni-directional antenna to said translator, the combination of means for assuring in-phase relationship between energy from said omni-directional antenna and from said directional antenna system in said translator device, comprising a pair of conductor lines forming at least a part of said second transmission line, said conductor lines differing in length by the spacing between said spaced antenna means, and being coupled together co-phasally at their ends arranged nearest said omnl-directional antenna and in phase opposition at their end remote from said one antenna, the combined electrical lengths of the transmission line including said pair of conductor lines as measured from said omni-directional antenna to said translator along both conductor lines of said pair being substantially equal to twice the length of said first transmission line.

HENRI G. BUSIGNIES.

REFERENCES CITED UNITED STATES PATENTS Name Date Busignies et al Mar. 9, 1943 Number 

